Renewable resources for producing electricity are often intermittent. Solar energy is a daytime event and the daytime solar-energy-concentration potential varies seasonally. Wind energy is highly variable. Falling water varies seasonally and is subject to extended drought. Biomass is seasonally variant and subject to droughts. Dwellings have greatly varying demands including daily, seasonal, and occasional energy consumption rates. Throughout the world, energy that could be delivered by hydroelectric plants, wind farms, biomass conversion and solar collectors is neglected or wasted because of the lack of a practical way to save energy or electricity until it is needed. Demand by a growing world population for energy has grown to the point of requiring more oil and other fossil resources than can be produced. Cities suffer from smog and global climate changes caused by the combustion of fossil fuels.
Also, burgeoning demands have developed for hydrogen, oxygen, carbon, and other products that can be provided by thermochemistry or electrolytic dissociation of feedstocks such as water, biomass wastes, or organic acids derived from biowaste. For example, the global market for hydrogen is more than $40 billion, and includes ammonia production, refineries, chemical manufacturing and food processing.
Electro-chemical production of fuels, metals, non-metals, and other valuable chemicals has been limited by expensive electricity, low electrolyzer efficiency, high maintenance costs, and cumbersome requirements for energy intensive operations such as compressive pumping of produced gases to desired transmission, storage, and application pressures. Efforts to provide technology for reducing these problems are noted and incorporated hereby in publications such as “Hydrogen Production From Water By Means of Chemical Cycles,” by Glandt, Eduardo D., and Myers, Allan L., Department of Chemical and Biochemical Engineering, University of Pennsylvania, Philadelphia, Pa. 19174; Industrial Engineering Chemical Process Development, Vol. 15, No. 1, 1976; “Hydrogen As A Future Fuel, by Gregory, D. P., Institute of Gas Technology; and “Adsorption Science and Technology”: Proceedings of the Second Pacific Basin Conference on Adsorption Science and Technology: Brisbane, Australia, 14-18 May 2000, By D. Do Duong, Duong D. Do, Contributor Duong D. Do, Published by World Scientific, 2000; ISBN 9810242638, 9789810242633.
Electrolyzers that allow hydrogen to mix with oxygen present the potential hazard of spontaneous fire or explosion. Efforts including low and high pressure electrolyzers that utilize expensive semi-permeable membrane separation of the gas production electrodes fail to provide cost-effective production of hydrogen and are prone to degradation and failure due to poisoning by impurities. Even in instances that membrane separation is utilized, the potential danger exists for membrane rupture and fire or explosion due to mixing of high-pressure oxygen and hydrogen.
Some commercial electrolyzers use expensive porous electrodes between which is an electrolytic proton exchange membrane (PEM) that only conducts hydrogen ions. (See Proton Energy Company and the Electrolyzer Company of Canada.) This limits the electrode efficiency because of polarization losses, gas accumulation, and reduction of available electrode area for the dissociation of water that can reach the interface of the electrodes and PEM electrolyte. Along with the limited electrode efficiency are other difficult problems including membrane ruptures due to the pressure difference between the oxygen and hydrogen outlets, membrane poisoning due to impurities in the make-up water, irreversible membrane degradation due to contaminants or slight overheating of the membrane, membrane degradation or rupture if the membrane is allowed to dry out while not in service, and degradation of electrodes at the membrane interface due to corrosion by one or more inducements such as concentration cell formation, galvanic cells between catalysts and bulk electrode material, and ground loops. Layering of electrode and PEM materials provide built in stagnation of the reactants or products of the reaction to cause inefficient operation. PEM electrochemical cells require expensive membrane material, surfactants, and catalysts. PEM cells are easily poisoned, overheated, flooded or dried out and pose operational hazards due to membrane leakage or rupture.
In addition to inefficiencies, problems with such systems include parasitic losses, expensive electrodes or catalysts and membranes, low energy conversion efficiency, expensive maintenance, and high operating costs. Compressors or more expensive membrane systems are situationally required to pressurize hydrogen and oxygen and other products of electrolysis. Corollaries of the last mentioned problem are unacceptable maintenance requirements, high repair expenses, and substantial decommissioning costs.
It is therefore an object of some embodiments of the present invention to provide an electrochemical or electrolytic cell, and a method of use thereof, for separated production of gases, including pressurized hydrogen and oxygen, that tolerates impurities and products of operation and address one or more of the problems with current methods set forth above.